Principal Uncertainty said:

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Jessup tells Kendrick "If Santiago doesn't make 4-6, 4-6 on his next report, I'm going to blame you." Markinson was there to hear those orders. And nowhere in there does Jessup use the phrase "Code Red" nor does he tell Kendrick to do anything against Marine rules. Markinson knew this. That's why he didn't want to testify. Markinson did not off himself because he was afraid to face Jessup. He did that, because if he was put on the stand, he knew he would have to testify that Jessup did NOT call for anything "Code Red". It's a subtle point that gets missed like Andy Dufrene's hammer being hidden in the biblical book of Exodus. So, there's that. But, that also makes Jessup's admission so much more powerful, because he admitted to something he was thinking even though he knows he never actually said those words.

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Did you actually watch the movie?
Markinson literally says "I wasn't strong enough to stop it."
It being the Code Red. He went to the Academy and Vietnam with Jessup and was horrified at himself for what he felt like was a betrayal of his old friend. That's why he killed himself. Not because of whatever you've concocted.